Fluidic half-adder

ABSTRACT

A fluidic gate having AND and exclusive OR outputs is disclosed in which control of the outputs is dependent upon the geometry of the interaction chamber and not upon the Coanda wall attachment phenomenon.

United States Patent 1191 Healey [4 1 Jan. 23, 1973 I FLUIDIC HALF-ADDER [75] Inventor: Anthony John Henley, State College,

[73] Assignee: Bell Telephone Laboratories, Incorporated, Murray Hill, NJ.

221 Filed: Sept. 8, 1970 211 Appl. No.: 70,131

[52] US. Cl ..l37/8l.5 [51] Int. Cl. ..F15c 1/10 [58] Field of Search ..137/8l.5

[56] References Cited UNITED STATES PATENTS Kepler et a1. ..l37/8l.5

3,608,573 9/1971 Buhrlon ..137/81.5 3,285,265 11/1966 Boothe ct 111. 1 37/8 l .5 3,107,850 10/1963 Warren et a1... ...l37/8l.5 X

3,192,938 7/1965 Bauer 1 137/815 3,443,575 5/1969 Hughes 1 137/8115 3,396,619 8/1968 Bowles et a1 ..137/81.5 X

Primary ExaminerSamuel Scott Att0rneyR. J. Guenther and Edwin B. Cave [57] ABSTRACT A fluidic gate having AND and exclusive OR outputs is disclosed in which control of the outputs is dependent upon the geometry of the interaction chamber and not upon the Coanda wall I attachment phenomenon.

7 Claims, 4 Drawing Figures PATENTEDJAH 23 I973 SHEET 1 0F 2 FIG./

FIG. 2

INI/ENTOR A. J. HEALEV PATENTEDJAH 23 ma 7 SHEET 2 OF 2 FLUIDIC HALF-ADDER This invention relates to fluidic logic devices and more particularly to fluidic half-adder gates.

BACKGROUND OF THE INVENTION Fluidic half-adder gates may be used to provide the logic functions of AND and OR." Such devices usually have two input nozzles from which pressurized fluid jets selectively issue. Either jet, appearing alone and exclusively of the other, will be received at a first fluid output. Thus an exclusive OR function is indicated by fluid flow from the first output. When both jets appear simultaneously, they interact to form a single resultant jet which is received at a second fluid output. Fluid flow from this second output is therefore indicative of an AND logic function.

Such devices are now in general commercial use and were disclosed in such prior patents as U.S. Pats. No. 3,107,850, issued to R. W. Warren et al. on Oct. 22, 1963, and 3,285,265, issued to W. A. Boothe et al. on Nov. 15, 1966. These prior devices depend upon 'the well-known wall attachment or Coanda phenomenon for their operation. Although these devices work effectively, this reliance on wall attachment imposes a size limitation when it is desired to miniaturize the device.

The reason why size limitations are imposed on wall attachment devices will become apparent by a close examination of the Coanda phenomenon. The phenomenon occurs when a fluid jet flows past a wall. The flowing jet traps ambient fluid between the jet and the wall. The entrained fluid is removed from the entrainment region by the passing jet, resulting in a reduction of pressure in the entrainment region. Turbulence increases the entrained flow and further decreases the pressure. The resulting pressure differential existing across the jet causes it to move closer to the wall (toward the lower pressure region).

Regenerative effects cause the jet to rapidly assume a stable state in which the unbalance forces are reduced to zero and a state of equilibrium is attained. When this point in time is reached, a minimum quantity of fluid will be trapped between the wall and the jet. At some point along the wall, the jet finally impinges. Beyond the point where impingement occurs, the jet is said to be attached to the wall.

Since the attaching forces are created by the jet flowing past a wall, it should be apparent that the longer the wall in the direction of the jet flow, the stronger the attaching force becomes. If the wall is very short, a very small attaching force is generated. With a small attaching force, the device becomes very sensitive to minor variations in supply pressure, etc. Therefore, a minimum length of attachment wall is necessary to provide a stable device having necessary switching reliability. Any efforts to further miniaturize the device by reducing the length of the wall below a minimum results in degradation of performance. Naturally, a device which does not rely on wall attachment for its operation is not limited by this restriction and so may be further miniaturized without altering the nozzle width or obtaining adverse results.

It should be noted here that device miniaturization can be accomplished either by a reduction in scale of the entire device or by selective geometric reduction in which only particular parts of the device are reduced in size. To insure wall attachment in miniaturized devices, the Reynold's number of the flow must be maintained above a predetermined minimum. Since the Reynolds number for a given fluid is essentially a function of the nozzle pressure and nozzle width, if the nozzle width is reduced, the nozzle pressure must be increased. In many applications, increased pressures are impractical, therefore the nozzle width cannot be significantly reduced. In wall attachment devices, a significant relationship exists between the width of the nozzle and the length of the attachment wall. For low Reynolds number operation, the attachment wall length relative to the width of the nozzle must be increased to maintain attachment stability. This results in additional wall drag and reduced pressure recovery with a resulting reduction in efficiency.

One of the fluid flow phenomena used in this invention is the phenomenon of knife-edge attachment. It is believed that knife-edge attachment can be maintained for flow conditions at low Reynolds number. This permits the device to be further miniaturized. Knife-edge attachment does not rely on a long length of attachment wall, merely a short cusp or knife-edge projection. The flow of the jet past the cusp creates a low pressure region in the area immediately upstream from the cusp. This low pressure region is effective to locate the flowing jet relative to the cusp.

It is an object of'my invention to provide a simple fluidic device for performing the half-adder logic functions which is capable of being effectively miniaturized due to its nonreliance upon the wall attachment phenomenon for its switching stability.

SUMMARY OF THE INVENTION In an illustrative embodiment of my invention two mutually perpendicular inputs communicate with an interaction chamber and exclusive OR and AND outputs. Each output is selectively produced depending upon the presence or absence of fluid flow from the inputs. The delivery of the interacting jets to the selected output is obtained as a result of the interaction chamber geometry and is not dependent upon wall attachment.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a device embodying my invention;

FIG. 2 shows the device of FIG. 1 with the fluid flow path indicated for a first input jet alone;

FIG. 3 shows the device of FIG. I with the fluid flow path indicated for a second input jet alone; and

FIG. 4 shows the device of FIG. 1 with the fluid flow path indicated for the two concurrent jets.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT Fluid logic devices may be constructed from any rigid, nonporous material, including glass, ceramic, plastic, and metal. Such devices generally comprise a base into which the desired passages are impressed or etched, and a cover providing a fluid-tight seal which is secured to the base by any of a number of methods, such as adhesives, fasteners, clamps, or the like. For ease of illustration, the drawings of FIGS. 1 m4 depict a device having a glass cover. This was done to permit the interior of the device to be shown without the confusing presence of cross-section lines. Thisshould in no way be interpreted as a limitation on the materials suitable for use in the device, since any rigid, nonporous material is applicable.

The particular device 100 illustrated in FIG. 1 comprises a first fluid input, passage 101 and a second fluid input, passage 102, which connect to independent fluid pressure sources (not shown). These sources provide pressurized fluid selectively, depending upon system conditions. The inputs 101 and 102 communicate respectively with nozzles 104 and 105 which are substantially perpendicular to each other. The nozzles act to generate a fluid jet when fluid pressure is present at the respective inlet. Either jet, appearing alone, will produce an output signal at receiver 114 and associated conduit 118. A signal at conduit 118 is indicative of an exclusive OR condition. The presence of concurrently generated jets produces an output signal at receiver 115 and associated conduit 119. A signal at conduit 119 is indicative of an AND condition.

The flow lines in FIG. 2 represent the jet pattern in device 100 when pressurized fluid is present at input 101 alone. An exclusive jet issues from nozzle 104 and flows toward cavity 103. Wall 107 is positioned away from the edge of the jet. As a result, the jet is unable to attach itself to wall 107. Since no wall is adjacent to the jet, the jet is unsupported and tends to continue in its original direction, diverging slightly as it flows. However, the proximity of a cusp 106 is effective to properly locate the jet and maintain it in position by knife-edge attachment. The jet is then deflected and redirected around curved wall 108 to cusp 109. When the jet reaches cusp 109 it has been redirected in a generally downward direction. The jet continues in this direction, with the jet diverging slightly since there is no adjacent wall to which the jet may attach and be supported.

The jet is deflected once again, this time by wall area 120, so that it is received at an output port, receiver 114. Fluid conduit 118 connects to receiver 114 with fluid flow through the conduit indicative of an exclusive OR condition, in this case flow from input 101 in the'absence of flow from input 102. Any loading effects, or flow resulting from impedance mismatches in the system, which could cause back pressure at receiver 114, are relieved by providing a vent 1 17.

If pressurized fluid is present at input 102, but no at input 101, the flow pattern of FIG. 3 is established. The pressurized fluid at input 102 generates a fluid jet from nozzle 105. The jet continues in a relatively straight direction, with the jet diverging slightly, since there is no adjacent wall to which the jet may attach and be supported. The flow of the jet past the knife-edge projection, cusp 121, is effective to create the knife-edge attachment previously described. This locates the jet in its proper position and maintains it there. The jet continues, to be delivered at receiver 114. Once again, the flow in conduit 118 is indicative of the exclusive OR condition, in this case the exclusive appearance of pressurized fluid at input 102.

Vent 117 again provides for the release of pressure under high load conditions so that the device is maintained at, or near, atmospheric or tank pressure and the integrity of the jet is maintained for all loading conditions.

When pressurized flow at both inputs 101 and 102 causes the generation of jets from nozzle 104 and nozzle 105 concurrently, the flow pattern indicated in FIG. 4 is obtained. The interaction of the two jets results in a momentum exchange in which the jets mutually deflect each other away from their original direction, resulting in the two jets combining into a single resultantjet.

Cavity 103 provides a pocket in which a circulation is established by the flow of the resultant jet. The circulation creates a higher pressure region in the vicinity of the two nozzles and prevents the resultant jet from entering the pocket and being deflected towards receiver 114. At the same time, a low pressure region is created at the opposite end of curved wall 108 in the vicinity of cusp 109. The phenomenon of knife-edge attachment" is effective to position the resultant jet relative to cusp 109 to be delivered at receiver 115. The presence of fluid flow through receiver 115, and into conduit 119 with which it communicates, produces the AND logic function and an indication that pressurized fluid is simultaneously present at inputs 101 and 102.

Despite the fact that the embodiment describes a passive device, it should also be apparent that the inventive principles are equally applicable to an active device in which either input is continuously present and the active output is determined by the presence or absence of a control jet at the other input.

What is claimed is:

l. A multistable fluidic device comprising a walled chamber,

a first nozzle for selectively issuing a first fluid jet into the chamber and away from the adjacent walls,

a second nozzle for selectively issuing a second fluid jet into the chamber and away from the adjacent walls but transverse to the first jet,

a first receiving channel connected to the chamber for receiving an issued jet and generating an output flow in a first stable state,

a second receiver channel connected to the chamber for receiving a jet and generating an output flow in a second stable state, and

a knife-edge projection positioned substantially normal to and impinging upon at least one issued jet, the jet being located thereby due to the pressure gradient established by the flow of the jet past the apex of the projection and being stabilized in that location by the attraction forces exerted by the established pressure gradient on the jet;

the nozzles and receiving channels being positioned relative to one another so that wall attachment does not occur as a jet travels between them.

2. A device in accordance with claim 1 wherein the second receiving channel is positioned to receive a resultant jet when the first and second jets concurrently issue.

3. A device in accordance with claim 1 wherein the first receiving channel is positioned to receive the first jet in the absence of the second jet.

4. A device in accordance with claim 3 further including means for deflecting the second jet from its normal direction in the absence of the first jet and for redirecting the second jet to be received by the first receiving channel.

5. A fluid logic device comprising a first fluid nozzle for selectively generating a first fluid jet;

a second fluid nozzle adjpcent to the first nozzle for selectively generating a second fluid jet substantially perpendicular to the first jet;

a walled chamber into which the generated first and second jets issue, the walls of the chamber adjacent to the nozzles being located away from the path of the generated jets;

a first fluid conduit for creating fluid flow, indicative of an exclusive OR condition, whenever either jet is generated in the absence of the other jet;

:1 second fluid conduit for creating fluid flow, indicative of an AND condition, whenever both jets are concurrently generated;

a first receiving channel positioned to receive the second jet in the absence of the first jet and to deliver the second jet to the first fluid conduit, the channel including a knife-edge projection positioned substantially normal to the second jet and effective to locate the second jet in the channel;

a wall of the chamber, positioned to deflect the first jet from its normal axis in the absence of the second jet, so that the deflected first jet is received by the first receiving channel; I

l a second receiving channel positioned to receive a resultant jet produced by the concurrent generation of the first and second jets and to deliver the resultant jet to the second fluid conduit, the channel including a knife-edge projection positioned substantially normal to the resultant jet and effective to locate the resultant jet in the channel; and

a vent passage connected to the chamber and extending substantially from the first nozzle to the first receiving channel for holding the chamber at substantially constant pressure to maintain the integrity of the fluid jets despite loading of the first and second conduits.

6. A multistable fluidic device comprising an interaction chamber;

a first nozzle for selectively issuing a first fluid jet into the interaction chamber;

a second nozzle for selectively issuing a second fluid jet into the interaction chamber and transverse to the first jet;

a first receiving channel communicating with the chamber for receiving either jet when it issues in the absence of the other jet and for generating a first stable output flow signal indicative of this state;

a second receiving channel communicating with the chamber for receiving both jets when they issue concurrently and for generating a second stable output flow signal indicative of this state; and

a first knife-edge for locating at least one issued jet,

the apex of the knife-edge being positioned substantially normal to and impinging upon the jet while both faces of the knife-edge are at substantial angles to the direction of travel of the jet, the jet being located thereby due to the pressure gradient established by the flow of the jet past the apex of the projection and being stabilized in that location by the attraction forces exerted by the established pressure gradient on the jet.

7. A device in accordance with claim 6 wherein the first knife-edge is positioned to locate the first et,

when it issues in the absence of the second jet, to be received by the first receiving channel; said device further including a second knife-edge positioned to locate the second jet, when it issues in the absence of the first jet, to be received by the first receiving channel;

a third knife-edge positioned to locate a resultantjet, when the first and second jets issue concurrently, to be received by the second receiving channel;

the nozzles and receiving channels being positioned relative to one another so that wall attachment does not occur as ajet travels between them; and

the knife-edges each being positioned so that the apex impinges on a jet while both faces of the knife-edge are at substantial angles to the direction of travel of the jet. 

1. A multistable fluidic device comprising a walled chamber, a first nozzle for selectively issuing a first fluid jet into the chamber and away from the adjacent walls, a second nozzle for selectively issuing a second fluid jet into the chamber and away from the adjacent walls but transverse to the first jet, a first receiving channel connected to the chamber for receiving an issued jet and generating an output flow in a first stable state, a second receiver channel connected to the chamber for receiving a jet and generating an output flow in a second stable state, and a knife-edge projection positioned substantially normal to and impinging upon at least one issued jet, the jet being located thereby due to the pressure gradient established by the flow of the jet past the apex of the projection and being stabilized in that location by the attraction forces exerted by the established pressure gradient on the jet; the nozzles and receiving channels being positioned relative to one another so that wall attachment does not occur as a jet travels between them.
 2. A device in accordance with claim 1 wherein the second receiving channel is positioned to receive a resultant jet when the first and second jets concurrently issue.
 3. A device in accordance with claim 1 wherein the first receiving channel is positioned to receive the first jet in the absence of the second jet.
 4. A device in accordance with claim 3 further including means for deflecting the second jet from its normal direction in the absence of the first jet and for redirecting the second jet to be received by the first receiving channel.
 5. A fluid logic device comprising a first fluid nozzle for selectively generating a first fluid jet; a second fluid nozzle adjacent to the first nozzle for selectively generating a second fluid jet substantially perpendicular to the first jet; a walled chamber into which the generated first and second jets issue, the walls of the chamber adjacent to the nozzles being located away from the path of the generated jets; a first fluid conduit for creating fluid flow, indicative of an exclusive OR condition, whenever either jet is generated in the absence of the other jet; a second fluid conduit for creating fluid flow, indicative of an AND condition, whenever both jets are concurrently generated; a first receiving channel positioned to receive the second jet in the absence of the first jet and to deliver the second jet to the first fluid conduit, the channel including a knife-edge projection positioned substantially normal to the second jet and effective to locate the second jet in the channel; a wall of the chamber, positioned to deflect the first jet from its normal axis in the absence of the second jet, so that the deflected first jet is received by the first receiving channel; a second receiving channel positioned to receive a resultant jet produced by the concurrent generation of the first and second jets and to deliver the resultant jet to the second fluid conduit, the channel including a knife-edge projection positioned substantially normal to the resultant jet and effective to locate the resultant jet in the channel; and a vent passage connected to the chamber and extending substantially from the first nozzle to the first receiving channel for holding the chamber at substantially constant pressure to maintain the integrity of the fluid jets despite loading of the first and second conduits.
 6. A multistable fluidic device comprising an interAction chamber; a first nozzle for selectively issuing a first fluid jet into the interaction chamber; a second nozzle for selectively issuing a second fluid jet into the interaction chamber and transverse to the first jet; a first receiving channel communicating with the chamber for receiving either jet when it issues in the absence of the other jet and for generating a first stable output flow signal indicative of this state; a second receiving channel communicating with the chamber for receiving both jets when they issue concurrently and for generating a second stable output flow signal indicative of this state; and a first knife-edge for locating at least one issued jet, the apex of the knife-edge being positioned substantially normal to and impinging upon the jet while both faces of the knife-edge are at substantial angles to the direction of travel of the jet, the jet being located thereby due to the pressure gradient established by the flow of the jet past the apex of the projection and being stabilized in that location by the attraction forces exerted by the established pressure gradient on the jet.
 7. A device in accordance with claim 6 wherein the first knife-edge is positioned to locate the first jet, when it issues in the absence of the second jet, to be received by the first receiving channel; said device further including a second knife-edge positioned to locate the second jet, when it issues in the absence of the first jet, to be received by the first receiving channel; a third knife-edge positioned to locate a resultant jet, when the first and second jets issue concurrently, to be received by the second receiving channel; the nozzles and receiving channels being positioned relative to one another so that wall attachment does not occur as a jet travels between them; and the knife-edges each being positioned so that the apex impinges on a jet while both faces of the knife-edge are at substantial angles to the direction of travel of the jet. 